The binding surface and affinity of monomeric and dimeric chemokine macrophage inflammatory protein 1 beta for various glycosaminoglycan disaccharides.

Chemokines comprise a family of proteins that function in the immune response to recruit leukocytes to sites of infection. This recruitment is believed to be carried out by the establishment of a chemokine gradient by the binding of chemokines to sulfated polysaccharides known as glycosaminoglycans (GAGs) located on the extracellular surface of endothelial cells. In the present studies, multidimensional NMR spectroscopy was used to study the interaction of monomeric and dimeric chemokine macrophage inflammatory protein (MIP)-1 beta variants with a series of differentially sulfated disaccharides. The data define a GAG binding surface, including both basic and uncharged residues such as Arg(18), Asn(23), Val(25), Thr(44), Lys(45), Arg(46), and Ser(47). Dissociation constants determined from these NMR studies consistently show for each disaccharide that dimeric wild type MIP-1 beta binds more tightly than monomeric MIP(9). Furthermore, analysis of the binding surface suggests that participation in the dimer of residues Met(3), Gly(4), and Ser(5) may be responsible for this higher affinity. These studies also indicate that the specificity of MIP-1 beta for particular GAG disaccharides is directly related not only to the degree of disaccharide sulfation but also to the position of the sulfate moiety, with O-sulfation at position 2 of the hexuronic acid unit and position 6 of the D-glucosamine being major determinants for binding.